Drought Tolerance in Mung Bean is Associated with the Genotypic Divergence,Regulation of Proline,Photosynthetic Pigment and Water Relation

Drought is one of the critical conditions for the growth and productivity of many crops including mung bean(Vigna radiata L. Wilczek). Screening of genotypes for variations is one of the suitable strategies for evaluatingcrop adaptability and global food security. In this context, the study investigated the physiological and biochemical responses of four drought tolerant (BARI Mung-8, BMX-08010-2, BMX-010015, BMX-08009-7), and fourdrought sensitive (BARI Mung-1, BARI Mung-3, BU Mung-4, BMX-05001) mung bean genotypes under wellwatered (WW) and water deficit (WD) conditions. The WW treatment maintained sufficient soil moisture(22% ± 0.5%, i.e., 30% deficit of available water) by regularly supplying water. Whereas, the WD treatmentwas maintained throughout the growing period, and water was applied when the wilting symptom appeared.The drought tolerant (DT) genotypes BARI Mung-8, BMX-08010-2, BMX-010015, BMX-08009-7 showed a highlevel of proline accumulation (2.52–5.99 mg g⁻¹ FW), photosynthetic pigment (total chlorophyll 2.96–3.27 mg g⁻¹FW at flowering stage, and 1.62–2.38 mg g⁻¹ FW at pod developing stage), plant water relation attributes including relative water content (RWC) (82%–84%), water retention capacity (WRC) (12–14) as well as lower watersaturation deficit (WSD) (19%–23%), and water uptake capacity (WUC) (2.58–2.89) under WD condition, whichprovided consequently higher relative seed yield. These indicate that the tolerant genotypes gained better physiobiochemical attributes and adaptability in response to drought conditions. Furthermore, the genotype BMX-08010-2 showed superiority in terms of those physio-biochemical traits, susceptibility index (SSI) and stress tolerance index (STI) to other genotypes. Based on the physiological and biochemical responses, the BMX-08010-2 wasfound to be a suitable genotype for sustaining yield under drought stress, and subsequently, it could be recommendedfor crop improvement through hybridization programs. In addition, the identified traits can be used as markers toidentify tolerant genotypes for drought-prone areas.